Tiny machines that patrol the body for invaders are one of nanotechnology’s favourite dreams. But a device made from a single molecule by a team of researchers in Israel sounds remarkably similar.

They have built a ‘DNA machine’ that detects a virus by reading its genome, and then produces an alarm signal, in the form of a visible glow…

The machine works like this. A separate DNA molecule called a hairpin, because its two ends stick together to form a loop, latches on to the pathogen’s DNA at one end and to the machine’s section A at the other. This triggers enzymes in the solution to build the DNAzyme encoded in section C, and then to snip it free.

A molecule known as hemin then activates the DNAzyme, which transforms another molecule called luminol, making it emit light.

It sounds complex, and it requires the presence of several enzymes, DNA building blocks, and other ingredients. But it all happens automatically.

So, are we comfortable calling this a “machine”, or not? Here’s some orientation from the useful-looking ISCID Encyclopedia of Science and Philosophy entry on molecular machines.

One of the authors, Itamar Willner, previously built an enzyme-based molecular computer for potential use inside the human body to assist with drug delivery. —Christine